Hprose\Client::subscribe PHP Method

    public function subscribe($name, $id = null, $callback = null, $timeout = null, $failswitch = false)
    {
        $self = $this;
        if (!is_string($name)) {
            throw new TypeError('topic name must be a string');
        }
        if (is_callable($id) && !is_callable($callback)) {
            $timeout = $callback;
            $callback = $id;
            $id = null;
        }
        if (!is_callable($callback)) {
            throw new TypeError('callback must be a function.');
        }
        if (!isset($this->topics[$name])) {
            $this->topics[$name] = array();
        }
        if ($id === null) {
            if ($this->id == null) {
                $this->id = $this->autoId();
            }
            $this->id->then(function ($id) use($self, $name, $callback, $timeout, $failswitch) {
                $self->subscribe($name, $id, $callback, $timeout, $failswitch);
            });
            return;
        }
        if (!is_int($timeout)) {
            $timeout = $this->timeout;
        }
        $topic = $this->getTopic($name, $id);
        if ($topic === null) {
            $topic = new stdClass();
            $settings = new InvokeSettings(array('idempotent' => true, 'failswitch' => $failswitch, 'timeout' => $timeout));
            $cb = function () use($self, &$cb, $topic, $name, $id, $settings) {
                $args = array($id);
                $self->invoke($name, $args, $settings)->then($topic->handler, $cb);
            };
            $topic->handler = function ($result) use($self, $name, $id, $cb) {
                $topic = $self->getTopic($name, $id);
                if ($topic !== null) {
                    if ($result !== null) {
                        $callbacks = $topic->callbacks;
                        foreach ($callbacks as $callback) {
                            try {
                                call_user_func($callback, $result);
                            } catch (Exception $ex) {
                            } catch (Throwable $ex) {
                            }
                        }
                    }
                    if ($self->getTopic($name, $id) !== null) {
                        $cb();
                    }
                }
            };
            $topic->callbacks = array($callback);
            $this->topics[$name][$id] = $topic;
            $cb();
        } elseif (array_search($callback, $topic->callbacks, true) === false) {
            $topic->callbacks[] = $callback;
        }
    }